1. Field of the Invention
The invention relates to a television motion detection arrangement having at least one television picture store for storing digital picture signal values related to picture elements of an interlaced television picture which on display is formed line-sequentially or horizontally and field-sequentially or vertically, a frame period comprising several field periods, and further including a picture signal value comparison circuit whose inputs are coupled to at least outputs of the store containing the picture signal values for producing picture signal value differences, to an absolute-value circuit coupled to outputs of the comparison circuit for supplying the picture signal value differences, to an adaptive threshold circuit coupled to outputs of the absolute-value circuit and to a threshold value-adapting circuit an output of which is coupled to a threshold value input of the adaptive threshold circuit for the supply of a threshold value which depends on the picture signal value differences, exceeding the adaptive threshold value being an indication of motion.
Such a motion detection arrangement can be used for various purposes. In the event of a television transmission channel having a bandwidth which is more limited than that of the television signal source, the motion detection can be used for bandwidth reduction. In the conversion of a television signal from one standard to another, the motion detection can be used to obtain an improved picture quality on display of the converted picture signal. In addition, the motion detection can be used during motion compensation for the case of a moving television camera. In all cases the detection can be combined with estimating the degree and/or the direction of the motion at a picture element of the television picture, considered or not considered across sub-regions of the television picture which comprise several, surrounding picture elements.
In all cases an appropriate detection whether there is motion or no motion in whatever degree or direction, is of basic importance. The adaptive structure of the threshold circuit results in known manner in an improved detection. Then, the adaptation can be effected on the basis of the picture signal value difference between an instantaneous picture element and the corresponding picture element one picture period earlier or earlier and later. However, at the occurrence of, on the one hand, details in the television picture having a high spatial frequency and, on the other hand, rapid motion corresponding to a high temporal frequency, it is still possible that faulty decisions as regards motion are taken, which, on display of the picture signal, results in an impermissible loss in picture quality. In practice, it has been found that a rapid motion transversely of a detail having a high spatial frequency may result in such a loss in quality.